Long-term effects of drought
Meeting the nutrient requirements of beef cattle
By Sam Wyffels
Developing a nutritional program that meets the needs of beef cattle throughout the production cycle and facilitates a return to cyclicity before the next breeding season takes an understanding of how cattle partition nutrients and the factors that impact their overall nutritional requirements. Typically, the beef production cycle can be broken down into four general stages:
calving to breeding
breeding to weaning
after weaning
pre-calving
Cattle utilize the nutrients they consume based on specific biological priorities: maintenance, growth, lactation, then reproduction. Due to reproduction being last on the list, it is often the first production-related factor impacted by inadequate nutrition.
As the post-calving period transitions into the breeding season, proper nutrition is paramount to ensure reproductive success. Nutritional deficiencies or imbalances during this time can have significant implications for reproductive performance, including delayed estrus, reduced conception rates and increased calving intervals.
During the period from post-calving through breeding the nutritional demands of cattle increase significantly to support milk production while also aiding in the recovery from labor. Peak lactation, and consequently peak nutrient requirements of cattle, typically happen between 60- and 80-days post calving. This can pose a unique challenge as cattle are expected to recover from having a calf and rebreed approximately 80-days post calving to maintain a 365-day calving interval.
For cattle that calved prior to April, peak lactation and nutrient requirements may come before the available forage can provide the nutrition required, necessitating careful management to ensure that cattle receive adequate nutrition. Therefore, if grazing pasture in early spring, producers may need to provide high-quality forages or supplements to support the increased requirements of lactation while on pasture to ensure animals have sufficient protein and energy to support lactation and recovery.
Additionally, nutrient requirements of cattle also vary based on the weight and milking potential of the cow. For example, a 1200-pound cow producing 20-pounds of milk a day requires 2.8-pounds of crude protein and 16.2-pounds of total digestible nutrients while the same cow that produces 30-pounds of milk a day requires 3.5-pounds of crude protein and 18.7-pounds of total digestible nutrients.
Failure to meet these requirements can limit the cow’s potential for milk production, and result in her drawing upon body nutrient stores to make up the deficit. This results in body weight and condition loss, which can cause a delay in returning to estrus and rebreeding (poor first-service conception rates). High-quality forages and supplemental feed may be necessary to meet the increased protein and energy requirements of lactating cattle.
Once breeding season concludes, and cattle are turned out to pasture, native range and pasture can generally meet the nutrient requirements of lactating cows in the northern Great Plains and Northwest during the peak of the growing season in late May and early June. However, pasture quality and availability can vary substantially year to year and throughout the grazing season, so continued attention to nutrition remains important to support herd health and productivity.
Weather conditions during the growing season have a profound influence on the growth and quality of forage. Precipitation, temperature and sunlight are the primary determinants of forage quantity and nutritional content. The fluctuations of these factors throughout the forage growing season influence the timing of maturity, with implications for nutrient content and digestibility. For example, abundant precipitation coupled with high temperatures and extended periods of daylight promotes plant growth and development, typically resulting in high moisture content in early spring forage followed by above average biomass production.
While high moisture content early spring forage seems to be good quality, these forages can frequently be below 25% dry matter, making it hard for cattle to consume enough forage to meet their nutrient requirements. Thus, high moisture content early spring forages are often called “washy.” However, these conditions have the forages primed for increased growth rates and biomass production as long as growing conditions remain ideal.
Although increased biomass production at first glance appears like a good thing, it comes with an increase in fiber and decrease in protein content, resulting in lower quality forage compared to average conditions. Conversely, under low precipitation and high temperature events, or drought conditions, forage maturity is often delayed with well below average biomass production.
There is a misconception that forage quality during a drought is poor, however, forage quality during a drought is usually greater than average. This is because of the delayed maturity of the forage under drought conditions, resulting in lower fiber and greater protein content than average growing conditions. Therefore, the challenges of grazing cattle under drought conditions are more related to finding enough forage availability for grazing rather than forage quality.
After weaning, cattle are no longer lactating, resulting in their most modest nutrient requirements in the production cycle. Thus, this stage of production represents the best time of the year to have the greatest impact on cattle condition through nutritional management. However, during this time most forages will hit maturity and go dormant. Dormant forage is high in fiber and deficient in protein, and likely doesn’t meet cattle nutrient requirements. Thus, grazing low quality dormant forage will likely result in decreased cattle performance without supplementation.
Providing supplements to grazing beef cattle during times of low forage quality can improve animal performance. Traditionally, concentrate feeds (cereal grains) were used to supplement energy on dormant forage diets, however, it has been found that grain-based supplements can have negative impacts on the digestibility and dietary consumption of low-quality forage. This is mainly because dormant forages are typically deficient in protein and high in fiber, which physically limits dietary consumption. Protein supplementation helps by stimulating the cattle’s protein starved rumen microbial communities and thereby enhancing digestibility and increasing dietary consumption to meet nutritional requirements with high fiber low-quality forages.
The final stage of production occurs approximately 60 days prior to calving. The majority of fetal growth happens during the period which results in an increase in nutrient requirements of the cow. Maintaining an optimal body condition score during this period is essential for maximizing reproductive efficiency of beef cattle.
It has been well established that cattle entering calving and breeding at body condition scores below 5 on a scale of 1-9, have substantially decreased first service conception rates, especially for high-producing cattle and 2- to 3-year-olds that still have individual growth requirements. This is because cattle with inadequate body condition at calving or those that have lost condition post calving take longer to recover from the stress of calving (90 days or more), resulting in a lower first service conception rates, a greater likelihood of open cows, an extended breeding season, an extended calving season the following year, and greater variability in calf weaning rates.
Cows with a body condition score of 5-6 are generally considered to be in ideal condition for rebreeding. Managing nutrition to achieve and maintain this target body condition score is crucial and may involve adjustments to feeding strategies based on individual cow needs and forage availability.
Navigating meeting cattle nutrient requirements in a dynamic system of changing forage quality and availability requires an understanding of the interactions of weather on forage conditions. Drought is a consideration that many producers have been faced with in recent years. During drought, the quantity of forage is often lacking making it difficult for cattle to consume enough forage throughout the year to meet nutritional needs, often necessitating feeding hay. However, during drought hay can be in limited supply and/or expensive, often leading to limit feeding animals to either “stretch” hay reserves or save money.
Recent research coupled with historic work in Montana found that cattle that were nutritionally stressed due to drought or no post-weaning to pre-calving supplementation can result in decreased cow performance and weight gains pre-calving that were still realized at weaning 300 days later. This suggests that long-term, or multiple year, droughts could have major consequences on cattle performance and conception rates. Thus, special consideration needs to be taken when feeding cattle hay, especially during drought conditions, to make sure body condition is not compromised during the pre-calving through breeding stages of production.
Nutritional management plays a central role in promoting the health, productivity and reproductive success of beef cattle throughout the post-calving, breeding, and turnout stages of production. By understanding the specific nutritional requirements of cattle during each phase and implementing effective feeding strategies, producers can optimize herd performance and profitability. Continued monitoring and adaptation to changing conditions are key to ensuring that cattle receive the nutrients they need to thrive throughout the production cycle.
Wyffels is an Extension beef specialist with Montana State University.
